In the future, use gandi.net or namecheap.com. They don't engage in such despicable practices.
McDonalds don't change the prices on the menu when they see you walk through the door looking particularly hungry.
I did not believe it at first, (thought the emails about paying someone else for my domains were a phishing scam) but I guess it did happen.
I have many godaddy=evil stories, the fact they don't enable letsencrypt / easy free ssl on their hosting / cpanel servers - it just makes them really shitty netizens on top of all the other shady things they have pulled over the years.
However, given domains are not securities and domain registrars are not FINRA members or registered securities broker-dealers, I don't think this is "frontrunning" in the sense that you're used to hearing the word.
So who knows if it's even illegal, and even if it is, who knows what recourse anyone has about it, given how quasi-legal and international the ownership of domains is.